Many lamps using the above-described type of a light emitting element as a light source adopt the configuration in which a light source unit is constituted by mounting one or more light emitting elements in a circuit board (e.g., a printed wiring board), and the light source unit is equipped in a lamp housing. For example, in a vehicle lamp for an automobile, the light source unit is equipped in the lamp housing in a state where the inside of the lamp housing is almost hermetic, in order to protect the light source unit from an external environment.
In this lamp, when the light source unit emits light, the temperature inside the lamp housing may increase due to heat generated from the light emitting element as the light source, and the temperature of the light emitting element may also increase accordingly. Thus, due to the so-called thermal runaway, the thermal reliability of the light emitting element may be deteriorated. Hence, it is required to dissipate the heat of the light emitting element to the outside of the lamp housing.
For example, Japanese Laid-Open Patent Publication No. 2014-146440 discloses a configuration in which a heat dissipating member is integrated with the rear side inner surface of a lamp housing opposite to the rear surface of a circuit board, and an opening is formed at the corresponding rear side inner surface to expose the heat dissipating member to the outside. According to this configuration, the heat generated from the light emitting element may be transferred to the heat dissipating member from the circuit board, and dissipated to the outside through the opening. In addition, Japanese Laid-Open Patent Publication No. 2011-192905 discloses a technique in which a conductive member also serving as a heat dissipating member is integrally embedded in a resin-made lamp housing.